Two signatures.

Made them using some tuts and render I found around here. I know they're kind of basic but I am new to GFX work. :)

http://i.imgur.com/t9W6r.png

http://i.imgur.com/7wA30.png

I would recomend useing soft brushes for lighting, while also us gradiant maps to mearge the layers. Also use a site like dafont to get betting fonts for your artwork.
Keep on creating

Crux

Your renders seem abit.. distorted in terms of proportion? Could just be me.. also id work on composition and an overall flow. They just seem to be all over the place. But they aren't bad for being new. Just gotta keep experimenting and practice!